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B H. JOHNSON.

E TELEPHONE. a No. 356,689. Patented Jan. 25, 1887.

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-EDWARD H. JOHNSON, OF NEYV YORK, N. Y.

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EPECIFICATION forming part of Letters Patent No. 356,689, dated January25, 1887.

Application filed December 8, 1883. Serial No.1l4,000. (ModclJ To ctZZwhom it may concern.-

Be it known that I, EDWARD H. Jonnson, of New York city, in the countyand State of New York, have invented a certain new and usefulImprovement in Telephones, of which the following is a specification.

The object I have in view is to produce a telephone whereby articulatespeech can be transmitted practically and successfully by means ofcontacts or electrodes of platinum or other metals, which instrumentwill maintain its adjustment and can be readily duplicated.

The instrument, having contact-electrodes of platinum arranged accordingto this invention, is also capable of use as a receiving-telephone Theinvention consists in providing means for locking the metalcontact-electrodes togcther positively, the construction being such thatthe impact of the sound-waves is taken by the contacts and not by thelocking device. This latter feature may besecured by the use of a loosescrew-thread, which, while drawing the parts positively together,permits the transmission of the impact of'the sound-waves to thecontacts, one of the contacts being carried by the diaphragm, while theother is rigidly supported from the case. Suitable insulation of theparts is also made, so that the electriccurrent will be directed throughthe Adjusting devices are provided to bring the contact-electrodes intoproper relation with each other.

Such being the principal features of the construction embodying myinvention, my theory of its operation, by which, however, I do not wishto be concluded, is as follows: Telephonetransmitters employingcontact-electrodes of platinum have not heretofore been practicallyoperative for the transmission of articulate speech on account of theextent of movement permitted at the contacts, which were forced so farapart by the impact of the fundamental sound -waves that they could notcome together again in time to respond from their normal position to asunicient number of the sound-waves to produce clear articulation at thereceiver, and such instruments, further, were permanently thrown out ofadjustment by the contraction and expansion of the diaphragm, due tochanges in temperature.

I have determined by my experiments that articulate speech can betransmitted electrically by the use of such instruments, provided thecontacts are maintained in such relation that they can respond from thenormal condition of the circuit to all the soundwaves, or a suflicientnumber of them to prod one clear articulation. This I accomplished withmarked success with instruments having diaphragms of felt or equivalentmaterial, as described in my former application No. 111,817, by reasonof the limited movement which such diaphragms permitted. I find,however, that a positive locking of the electrodes makes a superiorinstrument, and one which maintains its adjustment better and hasadvantages in mechanical construction. The positive locking together ofthe electrodes also prevents the separation of, the electrodes or thethrowing of the instrument out of adjustment by the expansion andcontraction due to changes in temperature, which takes place in thediaphrag m.

WVhcn electrodes of platinum areloclred positively together, I considerthat the impact caused by the sound-waves at the meeting surfaces of theelectrodes produces a rebound, which separates the meeting surfacesslightly, the distance, however small, being sufficiently great toaffect the current so as to enable the instrument to efficientlytransmit articulate speech.

My invention is illustrated in the accompanying drawings in a simpleform of instrument having platinum contacts and a single diaphragm,although the invention is equally applicable to more complex forms oftelephones.

Figure 1 is a sectional view of the instrument; Fig. 2, an elevation ofthe back of the same, showing theadjusting device; Fig. 3, an enlargedsectional view of the contacts and the means for locking them positivelytoget-her. 7

Like letters denote corresponding parts in all three figures. I

A is a diaphragm, of metal, mica, or other suitable material, which isclamped at its periphery in a suitable inclosing-case, B, which 'isshown as made of metal, but which may be of any insulating material. Thefront contact, a, of the instrument is the end of a platiw num screw, 0,while the back contact, I), of platinum is mounted on the end ofaturning spindle, D, extending through the case and prevented fromlongitudinal movement therein. This spindle is turned by a worm,E,engaging a worm-wheel, F, secured to the spindle. K

In the center of the diaphragm is clamped a metallic sleeve, G, thefront end of which is closed by an insulating block, 0, through whichpasses the platinum screw 0.

The rear end of the sleeve is provided with an internal screw-thread, d,with which engages a screw-thrcad, e, on the inner end of the spindle D.Thespindle D being turned into the sleeve G, the diaphragm is drawnbackward until the contacts a I) touch each other. The proper relationof the electrodes is determined by adjustment with the instrument incircuit. The screw'threads d and c are formed to fit loosely together,as shown in Fig. 3, so that while the contacts will be drawn positivelytogether and locked in that position by the screw-threads the impact ofthe sound. waves will not be transmitted through the screw-threads d 6,but through the contacts a b. The circuit-connections 1 2 are made withthe screw 6 and with the case.

In addition to the functions of the parts, as before explained, it maybe stated that the spindle D forms a rigid connection from the center ofthe diaphragm to the case, preventing the bulging of the diaphragm orits move ment in any way from the correct position.

What I claim is 1. In a telephone, the combination of an inelosing-ease,a diaphragm, a metal contact or electrode carried by said diaphragm, anda metal contact or electrode connected-rigidly with said case, saidcontacts or electrodes be ing locked positively together, substantiallyas set forth.

2. In a telephone, the combination of an inclosing-case, a diaphragm, ametal contact or electrode carried by said diaphragm, and

a metal contact or electrode connected rigidly.

their relation to each other, substantially as set forth.

4. 111 a telephone, the combination of an inclosing-case, a diaphragm, ametal contact;

or electrode carried by said diaphragm, a metal contact or electrodeconnected: rigidly with said case, and a device for lockingsai'dcontacts or electrodes positively togetherby means of a loosescrew-thread,substantially as set;

forth.

5. In a telephone,the combination of an inclosing-case, adiaphragm, acontact or electrode carried by said diaphragm, a contact or electrodeconnected rigidly to said; case, a sleeve locking said contacts orelectrodes positively together, and insulating material insulating saidcontacts or electrodes from said sleeve, substantially as set forth.

This specification signed and witnessed this 1st day of December, 1883.

EDWARD @H. JQH-NSON.

"Witnesses:

EDWARD II. P YATT, EDWARD G. ROWLAND.

